Alkylidenation of esters on solid support and traceless synthesis of 2-substituted benzofurans

Polymer-supported esters are smoothly converted into enol ethers using titanocene alkylidenes prepared by treatment of 2-tert-butyldimethylsilyloxybenzaldehyde diphenyldithioacetal with the low valent titanium species Cp2Ti[P(OEt)3]2. Treatment of the enol ethers with acid leads to the release of ketones from the Wang resin in high yield. Traceless solid-phase synthesis of 2-substituted benzofurans is achieved in a three-step termination procedure.